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LP3966: Short circuit protection delay

Kazuki Itoh
Genius 10730 points
Part Number: LP3966

Hi team,

My customer is using LP3966ES-3.3.

Could you let me know the short circuit protection delay of LP3966?
Also, it is difficult to interpret short circuit behavior from the sentence below.

> Once the power pass element shuts down, the control loop will rapidly cycle the output on and off until the average power dissipation causes the thermal shutdown circuit to respond to servo the on/off cycling to a lower frequency.

Could you please elaborate on this?

Best regards,

Kazuki Itoh

  • 0
    TI__Mastermind 18466 points

    Hey Kazuki-san, 

    it does not seem like the delay time was characterized, I will check to see if we have any timing diagrams we can use to approximate. 

    If a device is left in short circuit protection mode for too long, it will eventually trigger the thermal shutdown protection behavior - which are similar to each other but the latter responds at a lower frequency. 

    Best,

    Juliette

  • 0 in reply to Juliette
    TI__Genius 10730 points

    Hi Juliette-san,

    From the datasheet, in the event of a peak over-current condition, the shortcircuit control loop will rapidly drive the output PMOS pass element off.
    It looks like the short circuit event immediately turns off the pass FET, so I don't think it will eventually trigger the thermal shutdown.

    Could you please comment on this?

    Best regards,

    Kazuki Itoh 

  • 0 in reply to Kazuki Itoh
    TI__Mastermind 18466 points

    Hey Kazuki-san, 

    The PMOS turns off, but there is still power dissipation across the die through the output. Instead of working like a FET it begins to behave like a resistor, and eventually the head dissipated across the die will be enough to trigger thermal shutdown. 

    Best,

    Juliette

  • 0 in reply to Juliette
    TI__Genius 10730 points

    Hi Juliette-san,

    Thank you for the answer. I understand the behavior.

    Did you find the timing diagram to appriximate the prop delay?

    Best regards,

    Kazuki Itoh

  • +1 in reply to Kazuki Itoh
    TI__Mastermind 18466 points

    Unfortunately I did not find anything plots. I asked the validation team if they had a separate repository and am waiting back.